ECHINODERMA .1 The ix vaeppa, or " urchin-skinned " animals, have See also:

• LONG, GEORGE (1800-1879)
• LONG, JOHN DAVIS (1838– )

See also:

• DESOR, PIERRE JEAN EDOUARD (1811-1882)

Sladen and H. Theel respectively, in the See also:

• REPORT (O.Fr. report or raport, modern rapport, from O.Fr. reporter, mod. rap porter, Lat. reportare, to bring back, in poetical use only, of bringing back an account, news, &c.)

Hist. and in Proc. Zoo). See also:

• SOC

M. See also:

• DUNCAN
• DUNCAN, ADAM DUNCAN, 1ST VISCOUNT (1731-1804)
• DUNCAN, PETER MARTIN (1824-1891)
• DUNCAN, THOMAS (1807—1845)

Soc., 1884), the researches of H. See also:

• DURHAM
• DURHAM, JOHN GEORGE LAMBTON, 1ST EARL OF (1792–1840)

See also:

• BURY
• BURY, JOHN BAGNELL (1861- )

Univ., 1899), Theel (" Echinocyamus," Nov. See also:

• ACT (Lat. actus, actum)

See also:

• BARRANDE, JOACHIM (1799-1883)

Follmann, Jaekel, and especially B. Stiirtz (see Verhandl. nat. Vereins preuss. Rheinlande, Paldont. Abhandl., and Palaeontographica) ; while the multitude of See also:

• NORTH
• NORTH, BARONS
• NORTH, MARIANNE (1830—1890)
• NORTH, ROGER (1653-1734)
• NORTH, SIR THOMAS (1535?-16o1?)

(vol. vii.), or in any zoological See also:

• TEXT (Lat. textum, woven fabric, from texere, to weave)

I). That See also:

• PART

In some and orals 0 are formcrinoids which have no trace of a stern ing around the body-(e.g. Marsupites) a pentagonal plate is cavities r.pc and l.pc; found at the bbttom of the cup, where the p is the water-See also:

• PORE

3, D) and ophiurids (fig. 3, C) have a similar arrangement of plates on the dorsal (i.e. aboral) See also:

• SURFACE

Palaeontology lends no support to the See also:

• IDEA (Gr. Ibia, connected with i&eiv, to see; cf. Lat. species from specere, to look at)

Semon. There have always been many zoologists prepared to ascribe an ancestral See also:

• CHARACTER (Gr. xapareri7p, from xap&crew, to scratch)

(After Semon.) changes. The Pentactaea, at all events as it sprang from the See also:

• BRAIN (A.S. braegen)

More peculiarly Echinoderm features, in which the Pe atozoan nature is manifest, are the enclosing of the viscera in a ca fled and plated theca, for See also:

• PROTECTION

All the complicated structures of Blastoidea are evolved from a fairly simple type, which in its turn is linked on to one of the cystid orders. That the crinoids are all deducible from some such simple form as that above described under the See also:

• HEAD (in 0. Eng. heafad; the word is common to Teutonic languages; cf. Dutch hoofd, Ger. Haupt, generally taken to be in origin connected with Lat. caput, Gr. KerbOvi7)
• HEAD, SIR EDMUND WALKER, BART
• HEAD, SIR FRANCIS BOND, BART

The evolution of the modern Echinoidea from their Palaeozoic ancestors is also well understood, but in this case the ancestral form to which the palaeontologist is led does not at first sight present many resemblances to the Pelmatozoa. It is, however, characterized by simplicity of structure, and a See also:

• SHORT, FRANCIS JOB (1857– )

First, as already mentioned, it outlines the general features of the Dipleurula; secondly, it indicates the way in which this free-moving form became fixed, and how its internal organs were modified in consequence; but when we seek, thirdly, for See also:

• LIGHT

Evolution of the Echinoderms.-It is reasonable to suppose that the Coelomata—animals in which the body-cavity is divided into a gut passing from mouth to anus and a hollow (coelom) surrounding it—were derived from the simpler Coelentera, in which the primitive body-cavity (archenteron) is not so divided, and has only one See also:

• APERTURE (from Lat. aperire, to open)

Irtghe 1 /epos& coelom. anterior coelom mouth. !poste coelom, logical data that its special features were as follow:—The anterior coelomic cavity was wholly or partially divided, and from each half a duct led to the exterior, opening at a pore near the middle See also:

• LINE

left piste Aoelemior posterior coelom. coalom. side being the one chosen for a reason we cannot now See also:

• FATHOM

The two other openings are minute, and placed between those two; one close to the mouth is almost certainly the water-pore, while that nearer the anus is regarded as a genital aperture. Which of the coelomic cavities this last is connected with is uncertain, for there is considerable doubt as to the origin of the genital glands in the embryonic development of recent echino- derms. It seems clear, however, that there was but a single duct and a single bunch of reproductive cells, as in the holothurians, though perhaps bifurcate, as in some of those animals. The line between mouth and anus, along which these openings are situate, corresponds with the See also:

• PLANE

Origin-ally the calcareous substance of the plates (stereom) was pierced by irregular canals, more or less vertical, and containing strands of the soft tissue (stroma) that deposited the stereom, as well as spaces filled with fluid. In the former group (fig. 9) these canals became connected in pairs (diplopores) still perpendicular to the surface, and this structure, combined with that of the grooves, characterizes the order—Diploporita. In the latter group (fig. to) the canals, that is to say, the stroma-strands, came to lie parallel to the surface and to See also:

• CROSS

In this development of brachial extensions of the theca the genital organs were involved, and their ripe products formed at the ends of the brachia or in the branches therefrom. The remains of the original genital gland within the theca became the " axial organ " surrounded by the " axial sinus" derived from the anterior ccelom, and this again by structures derived from the right posterior coelom, which, as explained above, had been depressed to the aboral pole. These last structures formed a nervous sheath around the axial sinus with its blood-vessels, and became divided into five lobes correlated with the five basals (the " chambered organ ") and forming the aboral nerve-centre. Be-fore these changes were complete the Holothurioidea must have diverged, by the See also:

• ASSUMPTION, FEAST OF

The resemblance of the flooring-plates to the ambulacral ossicles of a starfish is so exact that one can explain it only by supposing similar relations of the water-canals and their branches (podia). On the thinly plated under surface of well-preserved specimens of Edrioaster are seen five interradial swellings (fig. II, B). These are likely to have been produced by the ripe genital glands, which may have extruded their products directly through the membranous integument of the under side. No other way out for them is apparent, and it is clear that Edrioaster was not permanently and solidly fixed to the sea-floor. Novr comes a great change, unfortunately difficult to follow whether in the fossils or in the modern embryos. We suppose some such form as Edrioaster, which appears to have lived near the See also:

• SHORE

Sollas and W. K. See also:

• SPENCER
• SPENCER, HERBERT (1820-1903)
• SPENCER, JOHN CHARLES SPENCER, 3RD EARL (1782-1845)
• SPENCER, JOHNPOYNTZ SPENCER
• SPENCER, WILLIAM ROBERT (1769-1834)

All living, and most extinct, Echinoderms show the following features, almost certainly due to an ancestral pelmatozoic stage: An incomplete radial symmetry, of which five is usually the dominant number, is superimposed on the secondary bilateralism, owing to the outgrowth from the mouth region of one unpaired and two paired ciliated grooves; these have a floor of nervous epithelium, and are accompanied by subjacent radial canals from the water-ring, giving off lateral podia and thus forming ambulacra, and by a perihaemal system of canals apparently growing out from coelomic cavities. All living Echinoderms have a lacunae, haemal system of diverse origin; this, the ambulacral system, and the coelomic cavities, contain a fluid holding albumen in See also:

• SOLUTION (from Lat. solvere, to loosen, dissolve)

Jaekel and F. A. Bather, start from such different points of view that no discussion of them can be attempted here, Following the narrative given above, we recognize a primitive group—Amphoridea—represented by Aristocystis (fig. 8). From this are derived the orders Diploporita (fig. 9) and Rhombifera (fig, io) and the class Edrioasteroidea, all which have already been described as steps in the evolution of the phylum. But there were also side-branches leading nowhere, and therefore placed in separate orders—Aporita and Carpoidea. Order I. Amphoridea.—Radial symmetry has affected neither food-grooves nor thecal plates; nor, probably, nerves, ambulacral vessels, nor gonads. Canals or folds when present in the stereom are irregular. Families: Aristocystidae (fig. 8) ; Eocystidae.

ctltated See also:

• PODIUM (Gr. lr66tov, diminutive of ?roils, foot)

Families: Anomalocystidae, Dendrocystidae. These correspond to Jaekel's Carpoidea Heterostelea ; he also includes, as Eustelea, our Comarocystidae and Malocystidae. Order 3. Rhombifera.—Radial symmetry affects the food-grooves and, in the more advanced families, the thecal plates; probably also the nerves and ambulacral vessels, but not the gonads. The food-grooves are exothecal, i.e. are stretched out from the theca on jointed skeletal processes (brachioles). These either are close to the mouth or are removed from it upon a series of ambulacral or subambulacral plates not derived immediately from thecal plates, or are separated from the oral centre by hypothecal passages passing beneath tegminal plates. The stereom and stroma become arranged in folds and strands at right angles to the sutures of the thecal plates; in higher forms the stereom-folds are in part specialized as ectini-rhombs. Families: Echinosphaeridae; Comarocystidae; acrocystellidae; Tiaracrinidae; Malocystidae; Glyptocystidae, with sub-famm. Echinoencrininae, Callocystinae, Glyptocystinae, of which 'examples are Cheirocrinus (fig. 1o) and Cystoblastus from which Jaekel deduces the blastoids; Caryocrinidae. Order 4. Aparita.—Pentamerous symmetry affects the food-grooves and thecal plates; probably also the nerves and ambulacral vessels, but not the gonads.

Food-grooves exothecal and circumoral. The stereom shows no trace of canals, folds, rhombs or diplopores. Family: Cryptocrinidae. 'Order 5. Diploporita.—Radial symmetry affects the food-grooves, and by degrees the thecal plates connected therewith, but not the interradial thecal plates; probably also the nerves and ambulacral vessels, but not the gonads. The food-grooves are epithecal, i.e. are extended over the thecal plates themselves without intermediate flooring; they are also prolonged on exothecal brachioles, which line the epithecal grooves. The stereom of the thecal plates may be thrown into folds, but the mesostroma does not so much tend to lie in strands' traversing the sutures, nor are pectini-rhombs or porerhombs developed; diplopores are always present in the mesostereom, but often restricted to definite tracts or plates, especially in higher forms. Families: Sphaeronidae; Glyptosphaeridae, e.g. Fungocystis (fig. 9) ; Protocrinidae; Mesocystidae; Gomphocystidae. The Protocrinidae See also:

• LEAD
• LEAD (pronounced iced)

Class II. BLAsTOIDEA.—Pelmatozoa in which five (by atrophy four) epithecal ciliated grooves, lying on a See also:

• LANCET (from Fr. lancette, dim. of lance, lance)

The stereom of the radials and deltoids on each side of the ambulacra is thrown into folds, See also:

• RUNNING

CRINOIDEA.—Pelmatozoa in which epithecal extensions of the food-grooves, ambulacrals, superficial oral nervous system, blood-vascular and water-vascular systems, coelom and genital system are continued exothecally upon jointed outgrowths of the abactinal thecal plates (brachia), carrying with them extensions of the abactinal nerve-system. ' The number of these processes is primitively and normally five, but may become less by atrophy. The brachia rise from a corresponding number of thecal plates, " radials (RR)." Below these is always a circlet, or traces of a circlet, of plates alternating with the radials, i.e. interradial, and called " basals (BB)." 'Through all modifications, which are numerous and vastly divergent, these elements persist. A circlet of radially situate infrabasals (IBB) may also be present. Below BB or IBB there follows a stem, which, however, may be atrophied or totally lost (see fig. I). The classification here adopted is that of F. A. Bather (1899), which departs from that of Wachsmuth and Springer mainly in the separation of forms with infrabasals or traces thereof from those in which basals only are present. These two series also differ from each other in the relations of the abactinal nerve-system. O. Jaekel (1894) has divided the crinoids into the orders Cladocrinoidea and Pentacrinoidea, the former being the Camerata of Wachsmuth and Springer (Monocyclica Camerata, Adunata and Dicyclica Camerata of the present classification), and the latter comprising all the rest, in which the arms are either free or only loosely incorporated in the dorsal cup.

In minor points there is fair agreement between the American, German and British authors. The families are extinct, except when the contrary is stated. Sub-class I. Monocyclica.—Crinoidea in which the See also:

• BASE

Order 3. Monocyclica Camerata.—Monocyclica in which the first, and often the succeeding, orders of brachials are incorporated by interbrachials in the dorsal cup, while the corresponding ambulacrals are either incorporated in, or pressed below, the tegmen by interambulacrals; all theca] plates united by suture, somewhat loose in the earliest forms, but speedily becoming close, and producing a rigid theca; mouth and tegminal food-grooves closed; arms pinnulate. Sub-order i. Melocrinoidea.—RR in contact all round ; first brachial usually quadrangular. Families: Glyptocrinidae, Melocrinidae, Patelliocrinidae, Clonocrinidae, Eucalyptocrinidae, Dolato- crinidae. Sub-order ii. Batocrinoidea.—RR separated by a heptagonal anal; first brachial usually quadrangular. Families: Tanaocrinidae, Xenocrinidae, Carpocrinidae, Barrandeocrinidae, Coelocrinidae, Batocrinidae, Periechocrinidae. Sub-order iii. Actinocrinoidea.—RR separated by a hexagonal anal; first brachial usually hexagonal. Families: Actinocrinidae, Amphoracrinidae. Sub-class II.

Dicyclica.—Crinoidea in which the base consists of BB and IBB, the latter being liable to atrophy or fusion with the proximale, but the aboral prolongations of the chambered organ are.always radial; new columnals may or may not be introduced at the proximal end of the stem. Order T. Dicyclica Inadunata.—Dicyclica in which the dorsal cup primitively is confined to the patina and occasional intercalated anals, and no other plates ever occur between RR (Grade: Distinct,) ; Br may be Incorporated in the cup, with or without iBr, but never rigidly, and their corresponding ambulacrals remain supra-tegminal (Grade: See also:

• ARTICULATA

Flexibilia.—Dicyclica in which proximal brachials are incorporated in the dorsal cup, either by their own sides, or by interbrachials, or by a finely plated skin, but never rigidly; plates may occur between RR. Tegmen flexible, with distinct ambulacrals and numerous small intes'ambulacrals; mouth and food-grooves remain supra-tegminal and open. See also:

• TOP (cf. Dan. top, Ger. Topf, also meaning pot)

IBB always the primitive 5. An anal plate always rests on the posterior basal; mouth and tegminal food- grooves closed; arms pinnulate. Families : Reteocrinidae, Dimerocrinidae, Lampterocrinidae, Rhodocrinidae, Cleiocrinidae. Class IV. EDRIOASTE ROIDEA.—Pelmatozoa in which the theca is composed of an indefinite number of irregular plates, some of which are variously differentiated in different genera; with no subvective skeletal appendages, but with central mouth, from which there radiate through the theca five unbranched ambulacra, composed of a See also:

• DOUBLE
• DOUBLE (from the Mid. Eng. duble, the form which gives the present pronunciation, through the Old Er. duble, from Lat. duplus, twice as much)

Grade B. ELEUTHEROZOA.—Echinoderma in which the theca, which may be but slightly or not at all calcified, is not attached by any portion of its surface, but is usually placed with the oral surface downwards or in the direction of forward locomotion. Food is not conveyed by a subvective system of ciliated grooves, but is taken in directly by the mouth. The anus when present is typically aboral, and approaches the mouth only in a few specialized forms. The aboral nervous system, if indeed it be present at all, is very slightly developed. The circumoesophageal water-ring may lose its connexion with the exterior See also:

• MEDIUM

4, Cucumariidae. (b) Without podia . Fam. 5, Molpadiidae. B. Without respiratory trees. (a) With podia . . Fam. 2, Elpidiidae. (b) Without podia . Fam. 3, Pelagothuriidae.

Order 2. Paractinopoda.—Neither radial canals nor podia. Tentacles supplied from circular canal. Fam. Synaptidae. It is admitted, however, that this See also:

• SCHEME (Lat. schema, Gr. oxfjya, figure, form, from the root axe, seen in exeiv, to have, hold, to be of such shape, form, &c.)

Synallactinae, Deimatinae, Elpidiinae, Psychropotinae), Holothuriidae (shallow water), Pelagothuriidae (pelagic). Order 2. Dendrochirota.—Tentacles simple or branched, never peltate; calcareous ring well developed, often bilaterally symmetrical; retractor muscles usually present; stone-canal opens internally; genital tubes in right and left tufts. Sub-order i. Apoda.—No tube-feet or papillae, but tentacular ampullae more or less developed. Mostly burrowers. Families: Synaptidae (sub-famm. Synaptinae, Chirodotinae, Myriotrochinae), Molpadiidae. Sub-order ii. Eupoda.—Tube-feet present, but tentacular ampullae rudimentary or absent. Families: Cucumariidae (climbers and crawlers), Rhopalodinidae (See also:

• BUR, or BURR (apparently the same word as Danish borre, burdock, cf. Swed. kard-boore)

STELLIFORMIA (=ASTEROIDEA Sensu lato).—Eleutherozoa with a depressed stellate body composed of a central disk, whence radiate five or more rays; this radiate symmetry affects all the systems of organs, including the genital. The radial water-vessels lie in grooves on the ventral side of flooring-plates (usually called " ambulacrals ") ; they and their podia are limited to the oral surface of the body and their extremities are separated from the Fm. t4. AlivingPentacrinid,Isocrinus See also:

• ASTERIA

A. With respiratory trees. (a) With podia . apical plates by a stretch of dorsal integument containing skeletal elements; the opening of the water-vascular system (madreporite) is not connected with a definite apical plate or system of plates. The starfish, brittle-stars and their allies (see STARFISH) have for the last fifty years usually been divided into two classes—Asteroidea and Ophiuroidea, each See also:

• EQUIVALENT

12, ) ; the rays as a See also:

• RULE

Paxillosa, Luidiidae, Astropectinidae (fig. 16); Archasteridae restr. Verrill, Porcellanasteridae, Chaetasteridae. Valvata, Benthopectinidae, Goniopec- tinidae, Plutonasteridae, Odontasteridae, Pentagonasteridae, Antheneidae, Pentacerotidae, Gymnasteriidae. Spinulosa, Poraniidae, Asterinidae. 2. Cryptozonia. — Unclassed Famm., t Sturtzasteridae (= Palaeocomidae See also:

• GREG, WILLIAM RATHBONE (1809–1881)

Velata, f See also:

• PAL, KRISTO DAS (1839–1884)

StUrtz, J. O. E. Perrier, and A. E. Verrill. Extinct families marked t. Grade A. Palophiurae.—Ambulacrals not yet forming complete vertebrae; plates of disk not yet specialized into mouth, radial or genital See also:

• SHIELDS, JAMES (181b-1879)

Stage b. Zygostichia.—Ambulacrals opposite and, except in Ophi- urinidae, fused; ventral arm-plates developed in some. Families: t Ophiurinidae, t Lapworthuridae, t Furcasteridae, f Palastropectinidae, t Eoluididae, t Palaeophiomyxidae. Grade B. Colophiurae.—Ambulacral pairs fused to form vertebrae with definite articular surfaces; mouth, radial and genital shields developed, though not all need be present in any one form. Order 1. Streptophiurae.—Rays simple and capable of coiling, since the vertebrae articulate by a See also:

• BALL (in Mid. Eng. bal; the word is probably cognate with " bale," Teutonic in origin, cf. also Lat. falls, and Gr. 7raXXa)
• BALL, JOHN (1585-1640)
• BALL, JOHN (1818-1889)
• BALL, JOHN (d. 1381)
• BALL, SIR ALEXANDER JOHN, BART
• BALL, THOMAS (1819- )

Suborder i. Brachyophiurae.—S pines short, simple, pointing towards the end of the arm. Families: Pectinuridae (=0phiodermatidae), Ophiolepididae. Suborder ii. Nectophiurae.—Spines may be variously elaborated and are set See also:

• MERE
• MERE, ADALBERT (1838-1909)

There are five prominent mouth-shields and a separate madreporite on the ventral surface. These genera attained the Colophiuran grade in respect of See also:

• EXTERNAL

EcHINOIDEA.—Eleutherozoa with a test of roughly circular, subpentagonal or elliptical outline, spheroidal, domed or flattened, of See also:

• PRIMARY

Order 2. Melonitoida.—Ambulacrals simple, each with two pores horizontally juxtaposed, in 2 to 18 columns; interambulacrals granulate with occasional tubercles, in 3 to I I columns, not more than one row passing on to the peristome; mouth central, with jaws, no external gills or sphaeridia; anus aboral, endocyclic. Families: Palechinidae (fig. 19, I), Melonitidae and Lepidesthidae, Silurian to Carboniferous. Order 3. Cystocidaroida.—Ambulacrals simple, each with one or two pores, which sometimes pass between rather than through the plates, in 2 columns; interambulacrals, uni- or multi-tuberculate, in numerous (say lo or more) columns, none passing on to peristome; mouth central with jaws, no external gills or sphaeridia; position of anus doubtful, acyclic, i.e. no apical system so far as known. Include only Echinocystis, Palaeodiscus and (?) Myriastiches, all Upper Silurian. Order 4. Cidaroida.—Ambulacrals simple, each with two pores horizontally juxtaposed, in 2 columns; interambulacrals unituberculate, in 2 to I I columns, some rows may pass on to the peristome; mouth central, with jaws, no external sills or sphaeridia; anus aboral, endocyclic. Families: Lepidocentridae and Archaeocidaridae (fig. 19, 2), Devonian and Carboniferous; Cidaridae (fig. 19, 3, 4), See also:

• PERMIAN

Order 5. Diademoida.—Ambulacrals generally See also:

• COMPOUND
• COMPOUND (from Lat. componere, to combine or put together)

8, Catopygus; Cretaceous. 3, A radiole of Cidaris; Jurassic. 4, Hemicidaris; See also:

• MID

Spatangoida.—Ambulacrals simple, with two pores juxtaposed, dorsal podia respiratory; interambulacrals bearing numerous small spines, none resorbed; mouth central or shifted forwards, with no jaws or external gills, sphaeridia numerous; anus exocyclic. As the mouth moves forward and the anus downward, the posterior interambulacrals between them are enlarged and strengthened so as to form a sternum. The order may therefore be divided into: (i.) Asternata, Famm. Echinoneidae, Nucleolitidae and Cassidulidae (fig. 19, 8); (ii.) Sternata, Famm. Collyritidae (fig. 19, 6), Echinocorytidae, Spatangidae (fig. 19, 7), Palaeostomidae, and Pourtalesiidae; Jurassic to Recent. . Order 8. Clypeastroida.—Ambulacrals simple or compound, with two pores juxtaposed, dorsal podia respiratory; interambulacrals multi-tuberculate, none resorbed; mouth central with flattened unequal jaws, reduced external gills, and few sphaeridia; anus exocyclic. Families: Fibulariidae, Laganidae, Scutellidae, Clypeastridae; Cretaceous to Recent.